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Contrasting pharmacological profiles for functional responses and binding in cells expressing the relaxin family peptide receptor 3 (RXFP3)
Author(s) -
van der Westhuizen Emma Therese,
Sexton Patrick M,
Summers Roger J
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.6.lb83-b
Subject(s) - relaxin , receptor , chemistry , reporter gene , neuropeptide , chinese hamster ovary cell , microbiology and biotechnology , biology , medicine , gene , biochemistry , gene expression
Relaxin‐3 is a neuropeptide involved in appetite regulation and stress behaviours in rats (Tanaka et al. 2005, McGowan et al. 2005), that is the cognate ligand for the Gi‐coupled RXFP3 receptor. In CHO‐K1 cells expressing human RXFP3 (CHO‐RXFP3), [ 125 I]‐INSL5/H3 relaxin chimera (100pM) bound to a single binding site, with competition observed with H3 relaxin (pIC 50 : 8.42 ± 0.25) but not H2 relaxin, porcine relaxin or INSL3 (n=6). However, in the same cells, inhibition of forskolin (30μM, 3 min) stimulated cAMP accumulation was observed not only with H3 relaxin (pEC 50 : 9.01 ± 0.27), but also with H2 relaxin (pEC 50 : 7.14 ± 0.59), porcine relaxin (pEC 50 : 7.41 ± 0.67) and INSL3 (pEC 50 : 7.45 ± 0.43) (n=10). We also established that RXFP3 activates ERK1/2 when stimulated with H3 relaxin (6.57 ± 0.78 fold/basal) and weakly with H2 relaxin (2.13 ± 0.74 fold/basal) but not with porcine relaxin or INSL3. The activation of ERK1/2 closely reflects the binding site characterized with [ 125 I]‐INSL5/H3 relaxin chimera, which is distinct from the site that leads to cAMP inhibition. Further characterization of RXFP3 signalling using reporter genes, revealed that H2 relaxin and porcine relaxin (all 0.1μM, 24h) could activate AP1 reporter genes, whereas INSL3 activated NFκB reporter genes (n=6). We propose that different relaxin family peptides interact with different binding sites on RXFP3, to activate distinct signalling pathways.